Population growth rate (Rt = Xt - Xt-1) of wolves versus ln-transformed density in the previous year (Xt-1). Solid lines indicate non-linear spline functions, and dashed lines indicate 95% confidence bands, estimated with generalized additive models. These plots suggest a threshold at ~3.25–3.50 wolves on a loge scale. The linear relationship below this threshold suggests weak density dependence while the relationship above this threshold suggests that density dependence is stronger at higher densities.
Ellis and Post BMC Ecology 2004 4:2 doi:10.1186/1472-6785-4-2